Digital watermarking

An image with visible digital watermarking. The text "Brian Kell 2006" can be seen across the center of the image.

A digital watermark is a message which is embedded into digital content (audio, video, images or text) that can be detected or extracted later. Such messages mostly carry copyright information of the content. It takes its name from watermarking of paper or money as a security measure. Yet the principle is different. Paper watermarks are visible to human recipient and he is expected to check the watermark to verify the authenticity of the document. However, in digital watermarking, the message is supposed not to visible (or at least not interfering with the user experience of the content), but (only) electronic devices can retrieve the embedded message to identify the copyright owner.

Such a watermark is supposed to be robust against typical transformation of the content. Thus the watermark needs to be reliably detectable, even is the content (e.g. the image) is cropped, rotated, compressed, etc.

Another form of digital watermarking is known as steganography, in which a message is hidden in the content without typical citizens or the public authorities noticing its precense. Only a limited number of recipients can retrieve and decode the hidden message.

Digital Watermarking Techniques

Watermarking Algorithms can be classified based on their embedding domain as follows:

• Spatial Domain:

The watermarking system directly alter the main data elements (like pixels in an image) by the watermark.

• Transform Domain:

The watermarking system alters the frequency transforms of data elements, this has proved to be more robust than the spatial domain.

• Feature Domain:

The watermarking system takes into account region, boundary and object characteristics. It presents better detection and recovery from attacks.

Applications

Digital Watermarking can be used for a wide range of applications such as:

• Copyright protection.
• Fingerprinting (Different recipients get differently watermarked content).
• Broadcast Monitoring (Television news often contains watermarked video from international agencies).
• Covert Communication (steganography).

See also

• ImageMagick (for adding visible watermarks)
• Copy attack
• Watermark (data file)

References

• Multimedia security : steganography and digital watermarking techniques for protection of intellectual property / Chun-Shien Lu, Editor.
• Multimedia security technologies for digital rights management/edited by Wenjun Zeng, Heather Yu, and Ching-Yung Lin.
• I.J. Cox and J.P.M.G. Linnartz, "Some general methods for tampering with watermarks", IEEE Journ. of Sel. Areas in Comm., Vol. 16. No. 4, May 1998, pp. 587-593.
• J.P.M.G. Linnartz, A.A.C. Kalker, G. Depovere, "On the design of a watermarking system: considerations and rationales", Information Hiding Workshop, Dresden, September 1999. Preliminary Proc. and Springer Verlag, LNCS 1768, pp. 254-269.
• J.P.M.G. Linnartz, A.C.C. Kalker, G.F. Depovere and R. Beuker, "A reliability model for detection of electronic watermarks in digital images", Benelux Symposium on Communication Theory, Enschede, October 1997, pp. 202-209.

Further reading

1. S. P. Mohanty, N. Ranganathan, and K. Balakrishnan, "A Dual Voltage-Frequency VLSI Chip for Image Watermarking in DCT Domain", IEEE Transactions on Circuits and Systems II (TCAS-II), Vol. 53, No. 5, May 2006, pp. 394-398.
2. S. P. Mohanty, K. R. Ramakrishnan, and M. S. Kanakanhalli, "A DCT Domain Visible Watermarking Technique for Images", in Proceedings of the IEEE International Conference on Multimedia and Expo (ICME) (Vol. 2), pp.1029-1032, 2000.
3. S. P. Mohanty, K. R. Ramakrishnan, and M. S. Kanakanhalli, "An Adaptive DCT Domain Visible Watermarking Technique for Protection of Publicly Available Images", in Proceedings of the International Conference on Multimedia Processing and Systems (ICMPS), pp.195-198, 2000.
4. S. P. Mohanty, K. R. Ramakrishnan, and M. S. Kanakanhalli, "A Dual Watermarking Technique for Images", in Proceedings of the 7th ACM International Multimedia Conference (ACMMM) (Vol. 2), pp.49-51, 1999.

External links

• Watermarking World – Premier site servicing the scientific Digital Watermarking community by Dr. Martin Kutter
• Digital Watermarking Alliance – Furthering the Adoption of Digital Watermarking
• Digital Watermarking & Data Hiding research papers at Forensics.nl
• StirMark – Watermarking robustness test developed by Markus Kuhn and Fabien Petitcolas.
• Directory of Books, Journals & Conferences on Digital Watermarking and Digital Watermarking Assessment Tools
• Slashdot article – "Warezed SoundForge Files In Windows Media Player"
• Information hiding homepage by Fabien Petitcolas
• Comparison of watermarking methods
• Watermarking used in monitoring television broadcasts
• Watermarking by Warping/Morphing of Videos - running studie to estimate the maximal possible strength of warping of videos without visible quality degradations to embed watermark information
• Watermark Tool – Free visible watermarking website.
• [1] - Jova, an mp3 digital watermarking system as designed and employed by FATdrop digital promo company.